ES2674405T3 - A steel wire cable for use in a drive system - Google Patents

Abstract

A steel wire cable for use in a drive system, comprising zinc coated steel wires or zinc alloys, said steel wires further comprising a liquid carrier coating, said liquid carrier coating comprising oxide particles of magnesium as a corrosion inhibitor, characterized in that said liquid carrier coating additionally comprises abrasive particles having a particle size between 5 and 50 micrometers, and on said steel wire cable at least 100 milligrams of oxide are present of magnesium per square meter of wire surface, said magnesium oxide and said abrasive particles being finely dispersed in said liquid carrier, said abrasive particles being intended to polish the surface of said wires.

Description

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DESCRIPTION

A steel wire cable for use in a drive system Field of the invention

The invention relates to the field of steel wire cables, in particular to steel wire cables that must withstand corrosive circumstances during operation. Such steel wire cables can be found in many drive systems, such as a window lift for automobile doors or a drive system for sliding doors, or for tarpaulin ceilings, or a garage door drive system or a elevator cable, to name just a few. The invention offers a more corrosion-resistant type of cable, while maintaining good fatigue properties and offering better friction properties.

Background of the invention.

Steel wire cables are, in many cases, the preferred means of transporting force and movement (i.e., work) at low cost over a distance, from meters to kilometers. Very flexible cables can be manufactured - so that the cable can accommodate small bending pulleys - using wires with fine diameters. When a cable is assembled from stretched and cold formed steel wires, the resistance of the cable can be increased, which allows the transmission of greater forces. Additionally, the modulus of elasticity is similar to that of steel and cable elongation can be minimized, which eliminates slack in the drive system. The cables may be designed to withstand the repeated bending, twisting or stretching movements that occur in such drive systems. In fact, steel wire cables are reliable since the fatigue limit can be predicted accurately, using tests that simulate the actual use of the cables. Finally, steel wire cables have a favorable coefficient of friction with respect to wear parts, a property that, in many cases, allows you to replace the bending pulleys with fixed cable guides, with the consequent and considerable savings in drive system costs.

Unfortunately, most types of steel tend to rust when they are subjected to conditions that increase corrosion (such as outdoor use, but also in interior elevator shafts or inside a car door). In this sense, corrosion is harmful and can dramatically reduce the expected level of fatigue, leading to premature and fatal fractures. Such a mechanism is known in the field as "corrosion fatigue", that is, the fatigue phenomena that occur when the dynamic load of the cable is carried out in a corrosive environment. Experts know certain common solutions to reduce such corrosion:

- Stainless steels can be used, which are less prone to corrosion (such as AISI 306, AISI 314). Unfortunately, such steels often only work well in static corrosive applications, that is, in which no dynamics are involved. When the cables are repeatedly flexed on the pulleys, the oxide layer that forms on the stainless steel undergoes continuous abrasion, which causes excessive wear of the filaments and reduced fatigue longevity.

- Perhaps the oldest solution is to use cables that are individually coated with a protective coating. In order not to adversely influence the remaining properties of the cable, said coating will preferably be metallic. In this regard, the most preferred coatings are those of zinc or zinc alloys, which are applied through a hot dip process on the steel wire. Intermediate layers of alloy are formed during hot dipping, ensuring good adhesion of the coating to the steel wire. Such coatings provide sacrificial corrosion protection to steel.

- encapsulation of the cord in a polymer is also a known technique. Such encapsulation must resist the dynamics of the drive system, to prevent the corrosive atmosphere from reaching the surface of the steel. WO 03/044267 describes such a cable. The solution provides excellent protection against corrosion, in combination with excellent fatigue properties, but it is somewhat stiffer, does not have too good friction properties, and is more expensive.

- the application of oils, greases, sludges or corrosion inhibiting gels. These gels must allow a series of properties in the steel wire rope and in many cases constitute a compromise between different properties (cost, environment, fatigue performance, etc.). An example can be found in US 6106741.

Therefore, the current state of the art for drive system cables is dominated by zinc-coated steel wire cables or zinc alloys, which are immersed in a lubricant. The thickness of the zinc coating or zinc alloys is chosen to resist a certain number of hours, in a corrosive environment. Such corrosion tests are widely known in the field as ISO 9227 (national equivalents are ASTM B117 or DIN 50021). In this test, samples, obtained from the manufacturer of the steel wire cable, are hung in a closed chamber filled with a nebula that is maintained at a relative humidity of 100%, at a temperature of 35 ° C. The atmosphere inside the chamber is saturated by means of

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a circulating spray of water, containing 5% by weight of NaCl. As described in ISO 9227.

Corrosion progress is monitored visually on a regular basis (for example, every 24 hours), and is classified into a series of classes ('light brown oxide spots',' light brown oxide spots', 'brown oxide spots dark ',' dark brown oxide spots' and '5% of the surface covered with dark brown oxide'). Thereafter, the number of hours in which the salt spray is maintained during this test is until "dark brown oxide spots" appear in the sample. At present, wire cables must withstand salt spray for a minimum of 72 hours before acceptance in the automotive industry.

The lubricant is chosen to optimize fatigue longevity. Estimates of fatigue longevity can be obtained by specific test procedures, which simulate the actual use of the cable in the drive system. Therefore, there are a number of patented test benches available to determine such fatigue longevity. A publicly available test is MIL-W-83420, which was widely used (and still used) to test 'aircraft cables'.

Another related technique is:

- JP63195282 describes a steel sheet with an organic film on a chromate layer, on a plated layer. The organic film comprises an oil (mineral, animal, vegetable, synthetic animal or synthetic plant) dispersed in water with wax, and a colloid or colloidal sun of one or more oxides such as SiO2, Cr2O3, Fe2O3, Fe3O4, MgO, ZrO2, SnO2 and AhO3 for greater operational capacity, greater corrosion resistance and greater adhesion to the steel sheet paint.

- JP2004124342 describes a window lift cable, comprising galvanized stainless steel wire cords. The cords are compacted before closing the cable. The cable may additionally be provided with a solid lubricant. A reduction in cable wear is claimed, due to the smoothed surface of the cable cords.

In the industry, there is a constant initiative to use thinner wire cables, with equal or greater resistance, in order to reduce the size of the drive systems while increasing the protection against corrosion and longevity to the fatigue. The use of known zinc or zinc alloy coatings implies a conflict between resistance and corrosion protection. Since the corrosion protection of the coating is roughly proportional to the thickness of the coating, a minimum thickness of the coating must be maintained to meet the corrosion protection requirements. However, as thinner and thinner wires are used, the coating occupies an increasing amount of the cross-sectional area of the wires. Since the coating does not increase the resistance of the wire, the thinner cables have a relative loss of resistance, compared to their thicker counterparts, due to this.

Summary of the invention.

Therefore, a first object of the invention is to provide a steel wire cable that overcomes the problems of the past. More particularly, an object of the invention is to provide a steel wire cable that combines good corrosion resistance without yielding to solidity. An additional objective is to provide a steel wire cable with improved friction properties. The inventors have investigated a particularly simple corrosion inhibitor, adapted to the specific use with drive system cables, which is efficient, economical, environmentally friendly and easy to apply: another object of their invention.

According to a first aspect of the invention, a steel wire cable is provided which is intended for use in a drive system. Wire cables of this type have a diameter of less than 5 mm, although sizes smaller than 3 mm are more preferred, while today sizes of 2 mm and 1.5 mm are more popular. The inventors believe that the trend towards wires of smaller diameter wires will continue, and anticipate that in the future cables with a diameter of 1 mm will be possible.

The steel wire cable is assembled with zinc coated steel wires or zinc alloys. The steel used to produce these wires is steel with a high carbon content, since a high strength is needed. Such steels have compositions according to the following guidelines: a carbon content between 0.35 and 1.15% in weight, preferably a carbon content between 0.60 and 1.00% by weight, a manganese content between 0.30 and 0.70% by weight, a silicon content between 0.10 and 0.60% by weight, a maximum sulfur content of 0.05% by weight, a maximum phosphorus content of 0.05% by weight. Microalloy with particular elements, such as chromium, nickel, vanadium, boron, cobalt, copper, or molybdenum in amounts ranging from 0.01 to 0.08% by weight, is not excluded, since this alloy can help reach levels of higher resistance.

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Some particularly popular coatings for these steel wires are:

- a technically pure zinc coating, so that it also includes unavoidable impurities

- an intentionally alloyed zinc coating, of which the following are provided in particular:

• zinc and aluminum alloys, such as those comprising 2 to 12% by weight of Al and a mischmetal such as cerium or lanthanum, the remainder being zinc. These are particularly preferred for their anti-corrosion properties (see, eg, EP 0 550 005 B1)

• Zinc and iron alloys, such as those that comprise 0.3 to 1.5% by weight of Fe, or those that comprise 15 to 25% by weight of Fe, the rest being zinc. Iron can originate from the steel substrate itself.

• a zinc alloy and tin. This is a coating attributed to favorable friction properties (see, eg DE 195 12 180 A1)

• Zinc and nickel alloys, such as those comprising 20 to 30% by weight nickel, the remainder being zinc.

It should be noted that the coating of the cable is generally carried out on an intermediate diameter steel wire, which is subsequently stretched through a series of matrices until finer diameters are obtained. During stretching, the tensile strength of the wire increases gradually, a clearly noticeable increase in high-carbon steel wires, such as those provided for in the present application. In general, steel wires have tensile strengths greater than 1750 MPa, usually above 2500 MPa, or more preferably above 2750 MPa, or even above 3000 MPa. These higher tensile strengths are necessary to be able to further reduce the diameter of the wire rope. The wire diameters for this type of cable rarely exceed 0.25 mm and, preferably, are below 0.22 mm, being even more preferred that they are below 0.15 mm. The use of many thin diameter wires results in a cable that is more resistant to fatigue than a cable with fewer wires that have a larger diameter.

The wires are assembled into braids, which may or may not be additionally assembled into wire wires. The usual configurations in the field are 7x7, 7x19, 19 + 8x7, 19W + 8x7, 7x8, 8x7, 8x8, 19 + 9x7, 1x3 + 5x7, to name just a few. For example, formula 7x8 designates a cable consisting of 7 braids, each of which consists of 8 wires. A braid consists of a core wire, around which 7 outer wires are helically twisted, with a certain pitch. Six of these braids are twisted around a core core braid, again with a defined step. The diameters of the outer wires are preferably chosen so that they easily fit around the core wire. Similarly, the diameter of the core braid can be chosen so that it adapts to the diameter of the outer braids. Braids can be produced layer by layer, twisting wires around intermediate braids, thus forming an exemplary configuration of a core wire surrounded by six wires, again surrounded by twelve wires, resulting in a 1 + 6 + 12 configuration, which is Abbreviated as a braid of 19 wires. A special case is one in which the diameters of the wires are chosen so that they fit perfectly, such as in a Warrington configuration (as in the core of the 19W + 8x7 type construction). The 19 wires are assembled together with the same step. Sometimes braids are compacted before wiring, or even full cables are compacted. Sometimes, a fiber replaces the core wire. The idea of the invention of the present application is equally applicable to all these variations.

Usually, the amount of coating on the wire is expressed in grams of coating per square meter of wire surface. Since the coating does not increase the resistance of the cable, it should be as thin as possible without compromising corrosion resistance. Examples of conventional coating quantities are - the number in brackets refers to the average thickness for a corresponding zinc coating having a density of 7140 kg / m3 - minimum 30 g / m2 (4.2 pm). However, lower amounts, such as less than 25 g / m2 (3.5 pm), or less than 20 g / m2 (2.8 pm), or even less, are more preferable for the present metal cable of the invention at 15 g / m2 (2.1 pm). The inventors believe that acceptable corrosion results could be obtained even with zinc coatings close to 5 g / m2 (0.7 pm) of zinc.

Although, in principle, there is no limitation for the type of process used to coat these steel wires, hot dip processes are preferred as they provide a solid coating that is welded to the steel. Due to the hot immersion an alloy layer will be formed between the steel and the coating, which entails additional protection for the steel. The coating described in EP 1 280 958 B1 is particularly preferred, in terms of strength and fatigue. A zinc coating with a reduced thickness of less than 2 micrometers (14.3 g of zinc per m2 of wire) is described, which includes the zinc and iron alloy layer, together with the associated process for coating the wires. Such a wire has a reduced thickness of zinc, which is favorable for obtaining a higher cable breaking load. Additionally, the roughness of the transition layer between zinc and steel is greatly reduced, resulting in improved fatigue properties. Unfortunately, the coating itself does not sufficiently protect against corrosion.

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However, the inventors have discovered that the lower corrosion resistance can be compensated by the use of a corrosion inhibitor, applied by means of a liquid carrier. To their surprise, they discovered that the compound best suited for this purpose is a very simple compound, namely magnesium oxide (MgO). Magnesium oxide (MgO) must be dispersed in fine particles in the carrier. The carrier only serves to distribute magnesium oxide evenly over the surface of the wire: the particles must be in close contact with the wire lining. The liquid carrier may remain in place, or it may evaporate: it has been observed that the corrosion-inhibiting positive effects still persist. Magnesium oxide allows thinner zinc coatings to be used, which implies advantages for greater strength and better fatigue, while maintaining and even improving corrosion resistance. Mutatis mutandis, magnesium oxide offers greater certainty against corrosion when used on wires with zinc coatings currently used.

Magnesium oxide (MgO) is a very common product that can be obtained through various processing routes. A first way is to heat magnesite (magnesium carbonate, a natural mineral deposit) in the presence of oxygen. A second route is to use brine containing MgCh, which is first converted to Mg (OH) 2 for purification through wet precipitation, followed by calcination to expel water. The last route is the most preferred. The resulting magnesium oxide (MgO) can be classified into different categories:

1. The "molten magnesium oxide" is calcined MgO, which melts in an electric arc furnace at temperatures

higher than 2750 ° C. It is the most stable and strongest of all types of magnesia.

2. "Sintered magnesium oxide" is calcined at temperatures between 1500 ° C and 2000 ° C, and has an area

surface area less than 0.1 m2 per gram.

3. The "synthesized magnesium oxide" is calcined at temperatures between 1000 ° C and 1500 ° C, and has an area

surface area of 0.1 to 1.0 m2 per gram.

4. "Caustic or slightly calcined magnesium oxide" is heated to 700 to 1000 ° C, and has an area

surface area of 1.0 to 250 m2 per gram.

The most preferred category is "slightly calcined", while the least preferred category is "synthesized." The "sintered" category is difficult to disperse and, therefore, is the least preferred. The "molten magnesium oxide" is too inert to be useful.

As a carrier, the most preferred is an aliphatic mineral oil. Aliphatic mineral oils are normally used to improve fatigue cable longevity by reducing wire friction when flexing on a pulley or wear part. Since they are to be applied on the wire cable anyway, they can be conveniently used as a carrier for the dispersion of magnesium oxide. Other possible liquid carriers are paraphenes and, more particularly, isoparaphenes, known for their easy evaporation.

The protective effect of magnesium oxide (MgO) against corrosion is already evident when tiny amounts are applied to the surface coated with zinc or zinc alloys. In fact, with a minimum of 100 milligrams of MgO per square meter of wire surface, positive effects can be identified, relative to the number of hours exceeded during the salt spray test. This is remarkable, compared to the amounts of zinc coating (usually present in amounts between 15,000 and 30,000 mg / m2). The effects increase linearly with the amount of MgO applied on the zinc coating or zinc alloys. Therefore, a 200 mg / m2 amount of MgO is most preferable. With higher amounts of MgO, 1,000 mg / m2 or 2,000 mg / m2 or even 4,000 mg / m2, they produce even better results. At present, no stabilization of the positive effects has been detected. One of the inventors hypothesizes that - without limitation to this theory - the presence of MgO in the zinc coating suppresses the cathodic reaction (that is, the electron consumption reaction) during the corrosion process. Due to this, MgO becomes a product that improves the passivation behavior of the zinc coating. Consequently, corrosion will only begin to be generated at those points that do not contain MgO. This would mean that MgO is a cathodic inhibitor, whose efficacy increases with the amount of magnesium oxide present.

Therefore, it has been observed that it is important to spread the magnesium oxide in fine particles on the surface of the wire, to obtain a uniform dispersion of the magnesium oxide flocs. The best way to achieve this is to use a finely ground magnesium oxide, with an average particle size between 1 and 100 micrometers, with 5 to 75 micrometers being most preferred. Magnesium oxide must be in physical contact with the zinc coating layer or zinc alloys, otherwise, corrosion protection will be less effective or non-existent.

In order to further improve this contact, the inventors added abrasive particles of approximately the same size (average particle size from 5 to 50 micrometers) to the liquid carrier as the magnesium oxide particles. The idea was that, by adding this abrasive, grinding of the surface of the zinc coating would occur, the magnesium oxide particles being better embedded. To their surprise, they discovered that the addition of said abrasive reduced the wear of the guide pieces, of polymer, of the drive system. Said guide pieces are generally composed of hard polymers, such as polyoxymethylene (POM) or polyamide (Nylon 6). For a description of the essay, reference is made to the document

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EP 0 550 005 B1, page 14, FIGURES 13, 14 and 15. Applicants consider - without being limited by this hypothesis - that abrasive particles not only activate the zinc coating, but also polish the surface of the wire, making it more smooth. Silicon carbide (SiC) is the most preferable abrasive, since it is cheap and all grain sizes can be easily obtained. Probably, other abrasives (quartz, cubic boron nitride, diamond and many others) would also be functional. It is also notable that these abrasive particles do not have a negative influence on the fatigue behavior of the steel wire rope. It has been observed that, in order to obtain said positive effects, an amount of between 0.1 and 10 is more than sufficient, preferably between 0.1 and 2 grams of SiC per kilogram of wire of metallic wires.

From the foregoing, it will be clear that the inventors have looked in particular for chemical elements and simple additives. Many of the commercially available corrosion inhibitors are commonly used, and are not specifically intended for wire cables for drive systems. As such, they contain more than five ingredients, many of which are complex and unavailable. The inventors have intentionally sought a simple solution, which above all is effective, cheap, environmentally friendly, and easy to implement. The number of constituents remains below five, namely: a liquid carrier (which may or may not disappear after application), magnesium oxide (MgO), silicon carbide (SiC) and, perhaps, some type of dispersant or floating agent.

According to an alternative, but not inventive, aspect of the application, a steel wire product is defined which comprises at least one steel wire, coated with zinc or zinc alloys. This steel wire has a peculiarity that a corrosion inhibitor is embedded in the zinc coating or zinc alloys, as a finely dispersed solid. Preferably, this corrosion inhibitor is present on the outer surface of the coating. More preferably, the solid corrosion inhibitor is stamped and pressed on the outer surface of said coating. Preferably this corrosion inhibitor is magnesium oxide (MgO).

According to a third, but not inventive, aspect of the application, a method of protecting a steel wire product is disclosed. The method begins with an intermediate diameter steel wire, provided with a zinc coating or zinc alloys. The steel and coating compositions are in accordance with the compositions described in the first aspect of the invention. In a wire drawing bench, preferably a wet wire drawing bench, the wire is sequentially stretched through progressively smaller dies, a technique common in the art. It is noteworthy from the method that the wire draws a finely dispersed corrosion inhibitor, towards one of the stretching dies. The corrosion inhibitor is printed on the outer surface of the coating, by the compression action of the matrix on the wire. The corrosion inhibitor can be applied to the wire in a matrix, e.g. ex. the input matrix (i.e. the largest) or the output matrix (i.e. the smallest). Or, the inhibitor can be supplied to the wire in two or more matrices, or in each matrix of the entire series of matrices.

The corrosion inhibitor can be provided in powder form. In that case, the corrosion inhibitor can be mixed in powdered soaps, which are common in the technique of drawing dry steel wires, in the form of solid lubricants. Such a powder mixture can be supplied together with the wire inside the die, guiding the wire through a soap box to the die inlet. The corrosion inhibitor can also be mixed with a liquid carrier, which is dragged by the wire towards the entrance of the die. It is important that the corrosion inhibitor comes into close electrical contact with the zinc coating or zinc alloys. Therefore, soap residues used in the stretching process should not insulate the corrosion inhibitor with respect to the zinc coating or zinc alloys.

Preferably, the corrosion inhibitor is magnesium oxide (MgO). It is preferable that the magnesium oxide powder has been finely ground, so that it passes through a 74 micrometer mesh.

Description of the preferred embodiments of the invention

The following describes a series of laboratory-scale tests, and in a production environment, which have been carried out on a cable of zinc-coated steel wires, type 19 + 8x7 with a diameter of 1.5 mm , for use in a window lift system. The cable has the following construction brand:

{[(0.15 + 6x0.14) 3.5 S + 12x0.14] s, 5 S + 8x (0.14 + 6x0.14) 4.8 z} 12 s

the different levels of square brackets indicate individual operations, the subscripts indicate the braiding lengths and the braiding directions. The cable has a linear mass of 9.78 g / m and a wire surface of 33.56 m2 / km of cable. If not indicated otherwise, the cable wires have been subjected to a technically pure zinc coating, hot dipped galvanized, of approximately 100 g per kg of cable of coated steel wires (i.e. 28 g / m2 or an average thickness of 3.9 pm).

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In a first series of tests, several substances were evaluated in the laboratory. Clean cable samples were coated with mixtures of compounds, with the standard aliphatic mineral oil used in the standard production cables. Six samples of each were hung in the salt spray test chamber, and visually inspected daily. The day the first dark brown spots appeared was noted. The result listed in TABLE 1 is the average (hSS PRM), the minimum (hSS min) and the maximum (hSS MAX) of the six samples. The presence of the compounds in the mixture was in accordance with the indicated weight percentages of the total mixture. Based on these findings, MgO was selected for further investigation.

TABLE 1

 No.

   Mix hSS PRM Hss min Hss MAX

 one

 Lube 84 72 96

 2

 Lubricant + 5% Benzimidazole 116 96 144

 3

 Lubricant + 10% magnesium oxide 324 312 336

 4

 Lubricant + 10% zinc oxide 108 96 120

 5

 Lubricant + 10% zinc carbonate hydroxide 116 96 144

 6

 Lubricant + 10% magnesium carbonate hydroxide 180 168 192

 7

 Lubricant + 10% hydrated zinc phosphate 84 72 96

 8

 Lubricant + 10% aluminum oxide 84 72 96

 9

 Lubricant + 10% hydrated magnesium silicate 84 72 96

 10

 Lubricant + 5% magnesium oxide + 5% hydrated magnesium silicate 156 144 168

 eleven

 Lubricant + 10% magnesium hydroxide 156 144 168

 12

 Lubricant + 10% magnesium stearate 132 120 144

 13

 Lubricant + 10% magnesium hydrogen phosphate 100 72 120

In a second series of laboratory experiments, the influence of MgO was determined by applying mixtures on the bare and degreased cable, with increasing amounts of magnesium oxide therein. Again, the samples were analyzed in the salt spray chamber, the results of which are summarized in TABLE 2.

TABLE 2

 No.

 Mix hSS PRM Hss min Hss MAX

 14

 Lube 108 96 120

 fifteen

 Lubricant + 15% MgO 556 432 648

 16

 Lubricant + 20% MgO 716 672 792

 17

 Lubricant + 25% MgO 884 816 1005

 18

 Lubricant + 30% MgO 828 816 840

 19

 Lubricant + 40% MgO 1140 1032 1248

 In a third series of experiments, a series of industrial scale mixtures was tested. Wire cables with two levels of amounts of zinc coating were tested: one with the standard coating of 28.0 g / m2 of wire surface, and one with a reduced layer of 24.3 g / m2. A different type of liquid carrier was also used, namely a liquid isoparaffin wax. Low molecular weight isoparaffins evaporate easily. In this case, the paraffin simply acts as a distributor for magnesium oxide on the surface of the wire wires. From the result it follows that the positive effects of MgO remain. TABLE 3

 No.

 Liquid carrier Zn (g / m2) mg / m2 MgO hSS PRM

 twenty

 Lube 24.3 0 65

 twenty-one

   459 120

 22

   885 136

 2. 3

   989 168

 24

   1138 256

 25

 28.0 0 85

 26

   72 144

 27

   272 248

 28

   504 248

 29

   1362 248

 30

 Paraffin 28.0 180 280

In a fourth series of experiments, an amount of silicon carbide (with a grain size between 8 and 32 microns) was added to the lubricant, in an attempt to activate the surface of the zinc coating by slight abrasion of the surface to the action of magnesium oxide. Although the action of silicon carbide did not deteriorate or

Corrosion resistance improved, measured in the salt spray chamber, surprisingly another positive effect was observed. It was observed that the shear wear of the fixed guide pieces, which are sometimes used to replace pulleys, practically disappeared: if the normal level of wear was 100, the influence of the SiC reduced it to 40, and even to 25 The test was carried out with a load of 120 N and a speed of the cable 5 with respect to the guide piece of 7.5 m / minute. The radius of curvature of the POM guide piece was 15 mm, with the cable covering 180 ° of the piece. The wear was evaluated after 5,000 round-trip cycles (ie 10,000 steps), in which the same 430 mm of cable was slid over the guide piece. No lubricant was added before the test.

The inventors want to emphasize that the invention is equally applicable to all types of steel wire cable configurations, and that its use is not limited to window lift systems but to all types of drive systems (sliding doors, sliding roofs, garage doors, curtain actuators, brake cables, clutch cables, door closure systems, this being a non-exhaustive list).

Claims (8)

5 10 fifteen twenty 25 30 1. A steel wire cable for use in a drive system, comprising zinc coated steel wires or zinc alloys, said steel wires further comprising a liquid carrier coating, said liquid carrier coating comprising particles of magnesium oxide as a corrosion inhibitor, characterized by that said liquid carrier coating additionally comprises abrasive particles having a particle size between 5 and 50 microns, and on said steel wire cable at least 100 milligrams of magnesium oxide per square meter of wire surface is present, said magnesium oxide and said abrasive particles finely dispersed in said liquid carrier, said abrasive particles being intended to polish the surface of said wires. 2. The steel wire cable of claim 1, wherein said liquid carrier is one selected from the group consisting of an aliphatic mineral oil, a paraphene, an isoparaphene, or mixtures thereof. 3. The steel wire cable of claim 1 or 2, wherein at least 200 milligrams of magnesium oxide are present per square meter of wire surface of said steel wire cable. 4. The steel wire cable of claim 1 or 3, wherein the average particle size of said finely dispersed magnesium oxide is between 1 and 100 micrometers. 5. The steel wire cable according to claim 4, wherein said finely dispersed magnesium oxide has a particle size of approximately the same size as said abrasive particles. 6. The steel wire cable according to any one of claims 1 to 5, wherein said abrasive particles are selected from the group consisting of silicon carbide, quartz, cubic boron nitride, diamond, and mixtures thereof . 7. The steel wire cable according to claim 6, wherein said abrasive particles are silicon carbide. 8. The steel wire cable according to any one of claims 1 to 7, wherein between 0.1 and 10 grams of abrasive particles per kilogram of said steel wire cable are present.